The collection of rare cases of cancer in patients with naturally-occurring immunodeficiencies from around the world has permitted investigators at the Immunodeficiency Cancer Registry (ICR) to describe the proportional excess of lymphomas and gastric carcinomas among this group of individuals. It is now well-recognized that lymphomas represent one of the major life-threatening complications of natural, as well as acquired T lymphocyte immunodeficiencies (e.g. associated with chronic immunosuppressive therapy following solid organ allografting, post marrow transplant immunodeficiency, or acquired immunodeficiency syndrome, AIDS). Compared to lymphomas in presumably nonimmunodeficient persons, lymphomas in immunodeficient patients are more likely to 1) occur with higher frequency at younger ages or with short latency following initiation of immunosuppression, 2) express diffuse and high grade malignant histology, 3) develop in extranodal sites such as the central nervous syste, 4) be associated with viral transformation, particularly involving Epstein Barr virus, and 5) be unresponsive to conventional treatment modalites. In the next 24 months the ICR aims to 1) initiate studies of the etiology of lymphomas in one particular immunodeficiency, Wiskott Aldrich syndrome, 2) continue ongoing collaborations and actively solicit new collaborations which will utilize the unique resources available through the ICR, and 3) continue the development of a detailed, validated computerized data base of ICR cases as a universal resource for future studies.